Joan Watson will get some bad news in the upcoming Season 6 of CBS’ “Elementary.”

In a recent interview with TV Insider, series star Lucy Liu revealed that Sherlock Holmes (Jonny Lee Miller) isn’t the only person close to Joan (Liu), who is suffering from a brain-related illness this season.

“She’ll learn her mother [Mary Watson played by Freda Foh Shen] has Alzheimer’s,” Liu said. “So someone else close to her is struggling with a mind that’s not what it used to be.”

Mary made her debut appearance in Season 1, episode 10, in which she tried to convince Joan to forgo her career as a sober companion and start taking up the life of a consulting detective. Mary then returned in Season 3, episode 17, in which Sherlock pointed out to Joan that her mother might be suffering from a mental health issue.

In the said episode, Mary saw her son Oren (Steve Park) kissing a woman who was not his wife. But instead of confronting Oren herself, Mary asked Joan to make things right. When Oren denied the cheating allegations, Sherlock told Joan to consider the possibility that Mary might have started to forget things. Because Joan was in denial at that time, Sherlock reached out to Mary himself and convinced her through an elaborate tale that she forgot Joan’s birthday.

Also in the new season, Joan will lose someone who was very close to her once upon a time. Executive producer Rob Doherty told TVLine last October that “this person made certain assessments regarding the decisions Joan has made as a professional,” so his or her death is going to give Joan a reason “to look at choices she’s made and choices that she has right in front of her: Might she be a more complete person if she weren’t in a partnership with Sherlock Holmes?”

As for what viewers can expect from Sherlock this season, Liu said that Joan’s partner will be diagnosed with a brain injury and will meet a “clever man … who wants to take advantage of the fact that Sherlock is not quite on his toes.”

“Elementary” Season 6 premieres on Monday, April 30 at 10 p.m. EDT on CBS.

Lucy Liu as Joan
“Elementary” star Lucy Liu revealed that Joan Watson will find out that her mom has been diagnosed with Alzheimer's disease in Season 6 of the CBS series. CBS